The present invention relates to the packaging industry, and more particularly to a method and system for making an embossed multi-layer flexible packaging material.
The art of embossing entails applying pressure to a material and thereby causing the formation of a raised pattern in the material. Prior art methods usually include the use of a rigid embossing roller and a soft backing roller to achieve the final embossed product. However, there are significant drawbacks to using the prior art methods for embossing flexible packaging materials.
When a flexible packaging material is to be used for the enclosure of food products or other perishables, the barrier properties of the packaging material are of great importance. It is usually desired that the packaging material have oxygen barrier properties, moisture barrier properties, light barrier properties or a combination of these properties. Several prior art methods of embossing of a packaging material involve embossing the flexible packaging material after it is laminated. These prior art methods are unsatisfactory in that they disrupt the material having the barrier properties and thereby greatly diminish those properties.
In an effort to solve the problems associated with embossing a packaging material after it is laminated, prior art methods arose wherein a second layer of the packaging material is embossed and then laminated to a barrier layer. The disadvantage of this method, however, is that the process of laminating subsequent to embossing results in a flattening or ironing out of the embossed pattern.
Therefore, what is needed in the art is a method and a system for making embossed packaging materials that do not greatly disrupt the desired barrier properties of the packaging material and/or do not substantially flatten the embossed pattern on the flexible packaging material.
The present invention provides a novel method and system for extrusion embossing that remedies the deficiencies of prior art methods of embossing. In particular, the present invention provides a method and system for embossing a multi-layer flexible packaging material whereby one layer is embossed simultaneously with the extrusion of an adjacent layer and the lamination of an additional layer.
In one embodiment of the present invention, the system comprises an embossing roller and an anvil roller positioned against the embossing roller so as to form a nip between the embossing roller and the anvil roller, a means for moving the flexible packaging material through the assembly of rollers, and an extrusion die. Preferably, the system also comprises a pressure roller for pressing the embossing roller against the anvil roller.
A three-layered flexible packaging material is formed and embossed using one embodiment of the present invention in the following manner. A first layer of pre-formed material is fed in sequence to a pressure roller, an embossing roller and a nip between the embossing roller and an anvil roller. Simultaneously, a third layer of pre-formed material is fed in sequence to the anvil roller and the nip between the embossing roller and the anvil roller. Also simultaneously, a molten sheet of a second layer is extruded from an extrusion die and deposited between the first layer and the third layer at the location of the nip of the embossing roller and anvil roller.
The method and system of the present invention provide many advantages over the prior art. For example, the present invention avoids or limits the loss of barrier properties in a flexible packaging material that typically accompanies the embossing of the material. The present invention avoids or limits the loss of the embossed pattern on the flexible packaging material during production processing of the material. It is also expected that the present invention reduces the coefficient of friction of the surface of the flexible packaging material. Reducing the coefficient of friction results in the improved processing of the material on a xe2x80x9cForm, Fill and Sealxe2x80x9d (F/F/S) machine and possibly reduces or ameliorates the need to incorporate slip agents into the material. Finally, it is expected the present invention improves the xe2x80x9chandxe2x80x9d of stiffness of the embossed flexible packaging material and thereby permits the down gauging of the material""s thickness.
Other objects, features and advantages of this invention will be apparent after a review of the following detailed description of disclosed embodiments, the figures and the appended claims.